It was the engagement seen 'round the world Wednesday night on American Idol, so how did Ace Young manage to pull off his surprise proposal to fiancée Diana DeGarmo?

With a little help from his Idol family, it turns out.

"I called [producer] Nigel [Lythgoe] directly last week and said, 'I want to do this. I'm going to do this. Is there any way I could do it at the show?' " Young, 31, told PEOPLE at the Ford-sponsored American Idol season 11 finale post party. "He said 'Yes, I'm not going to tell anybody until the day of ... [and] I want you to figure it out with Ryan [Seacrest]."

Seacrest called them both to the stage and said, "dim the lights," like he does at every results show. As the elimination night music played, Young, 31, said, "This has always been home to us and I felt that this would be the perfect place to ask a simple question."

Nearly two years after falling in love, American Idol alumni Ace Young and Diana DeGarmo are opening up about their relationship.

Season 5 heartthrob Young, 31, and season 3's runner-up DeGarmo, 24, met in the spring of 2010 when both signed on to costar in the Broadway revival of the musical Hair.

"We became best friends through Hair, ironically not through Idol," says DeGarmo, who now plays as a New Jersey Mob boss's daughter on the CBS soap The Young and the Restless. "It just blossomed into a beautiful relationship."

Now comes the real challenge for American Idol runner-up Diana DeGarmo: making it as a pop star. Only 17, this season's No. 2 (she lost to Fantasia Barrino) already has a single, "Dreams," a summer tour with the Idol crew and the perfect date to sing the national anthem – July 4 – for her home state baseball team, the Atlanta Braves. PEOPLE recently caught up with DeGarmo before her guest spot during the Oxygen network's Custom Concert with LeAnn Rimes, and got the dish on her plans for a funky, Prince-filled summer.

By this time Thursday, everyone will know the new American Idol winner. If the program's judges and TV critics had their way, based on Tuesday night's televised showdown, Fantasia Barrino would already be wearing the crown.

It's the final showdown for American Idol 3: Fantasia Barrino and Diana DeGarmo will go head-to-head on Tuesday, with the big winner announced Wednesday during the FOX talent hunt's two-hour live season finale.